TLV5639C, TLV5639I

2.7 V TO 5.5 V LOW POWER 12-BIT DIGITAL-TO-ANALOG

CONVERTERS WITH INTERNAL REFERENCE AND POWER DOWN

SLAS189 – MARCH 1999

13

POST OFFICE BOX 655303

APPLICATION INFORMATION

TLV5639 interfaced to TMS320C203 DSP

hardware interface

Figure 13 shows an example of the connection between the TLV5639 and the TMS320C203 DSP. The only

other device that is needed in addition to the DSP and the DAC is the 74AC138 address decoding circuit . Using

this configuration, the DAC data is at address 0x0084 and the DAC control word is at address 0x0085 within

the I/O memory space of the TMS320C203.

LDAC is tied low so that the output voltage is updated on the rising WE edge.

A2

A3

A4

A6

IS

D(0–11)

5 V

A

B

C

G1

G2A

G2B

CS

D(0–11)

Y1

WE

REF

To Other Devices Requiring

Voltage Reference

OUT

LDAC

WE

RLOAD

TMS320C203

74AC138

TLV5639

12

REG

A0

Figure 13. TLV5639 to TMS320C203 DSP Interface Connection

software

Writing data or control information to the TLV5639 is done using a single command. For example, the line of

code which reads:

out

62h,

dac_ctrl

writes the contents of address 0x0062 to the I/O address equated to dac_ctrl (0x0085, the address where

the DAC control register has been mapped).

The following code shows how to set the DAC up to use the internal reference and operate in FAST mode by

a write to the control register. Timer interrupts are then enabled and repeatedly generated every 205

µs to

provide a timebase for synchonizing the waveform generation. In this example, the waveform is generated by

simply incrementing a counter and outputting the counter value to the DAC data word once every timer interrupt.

This results in a saw waveform.